1. Field of the Invention
This invention relates generally to devices for dampening vibration, and more particularly to a device that, when inserted between a set of strings of a game racket, will dampen the vibrations experienced by the strings (and the player) when the strings contact a game ball. Additionally, the device may be inserted between the spokes of a bicycle wheel such that vibrations experienced by the wheel during use will be dampened before reaching the frame of the bicycle.
2. Brief Description of the Prior Art
In strung, hand held game rackets, vibrations are produced when the player causes the racket to strike a ball. These vibrations begin in the area of the interwoven string diaphragm where the ball is struck (the striking surface), radiate outwardly through the string network to the frame of the racket, and then on to the hand and arm of the player. Exposure to vibrations over a long period of time can cause injury to the player's hand, wrist and arm. To avoid this type of injury, it is desirable to reduce such string vibrations before they reach the racket frame.
Early efforts to dampen vibrations were directed to the racket's construction. Carbon and graphite racket frames replaced the traditional wood frames, and the shape of the racket frame was experimentally modified. Yet none of these changes amply reduced the vibrations felt by the player. Natural catgut used for the racket's strings was found to produce lower levels of vibration than plastic strings, but players preferred the higher performance plastic strings which, unfortunately, produce a higher level of vibration.
After the early efforts to reconstruct the racket had failed, inventors created shock absorbing inserts to be placed between a set of strings for dampening vibrations. The vibration dampening inserts in the prior art recognized that mechanically coupling or mechanically isolating a set of strings by inserting a vibration absorbing material between them, resulted in a dampening of the vibrations that flow through the strings when the striking surface of the racket hits a ball.
U.S. Pat. No. 4,180,265 involves a dampening device that couples two parallel strings or one longitudinal string and one transverse string together. The length of the device is smaller than the distance between the strings, causing the distance between the strings to be slightly reduced at the dampening device. The vibration from the strings is dampened because the coupled strings are detuned relative to each other and also because the elastomeric material that the device is made from has inherent viscoelastic dampening properties. This type of device is usually an integral part of a racket. Therefore, it must be woven into the string diaphragm at the time the racket is manufactured.
Converse to the mechanical couple, U.S. Pat. No. 4,609,194 illustrates a vibration dampening device that, when inserted between a set of strings within a racket frame, mechanically isolates the strings and absorbs the vibrations flowing through the string diaphragm when a ball is hit. This is achieved by inserting a compressed block of viscoelastic foam between two parallel longitudinal strings and at least one adjacent transverse string, and then releasing the foam block, allowing it to expand to its natural shape. The expanded foam presses outwardly on the engaged strings urging them away from one another, thus mechanically isolating them. When vibration is produced in the striking surface of the racket, the foam from which the device is made absorbs the vibrations and turns the mechanical vibrational energy into heat energy which is dissipated.
After insertion, the foam block expands in all directions where it is unrestrained by the racket strings. The majority of the foam expands in a direction generally normal to the direction of the strings, causing an interruption in the flat plane of the racket face that is created by the interwoven string diaphragm. When a player swings the racket and hits a ball at the point on the interwoven string diaphragm where this type of device is inserted, the device will interfere with the normal travel of the ball and misdirect the struck ball, thereby hampering the player's skill. Additionally, these foam devices are rapidly destroyed under normal wear and tear.
The spokes of a bicycle wheel experience vibrations during use similar to the vibrating strings of a game racket. The spoke vibrations from the front wheels are transmitted to the front forks of the bicycle frame and then on to the main frame of the bicycle. These vibrations affect the rider's arms as they continue through the frame onto the handlebars. Further, the vibrations from the rear wheel passes through the rear forks to the seat of the bicycle causing the rider further discomfort.